The Eastern Ghouta, home to up to 400,000 people, is the last rebel stronghold close to Damascus.

Earlier this year, it was designated as one of four "de-escalation zones" agreed by the government's close allies, Russia and Iran, together with rebel-backer Turkey.

Despite that, the area has continued to come under bombardment. Troops and allied militiamen have also shut many of the routes used to smuggle in food and medicine, leaving residents dependent on irregular aid deliveries.

Two weeks ago, following a surprise ground offensive by jihadist rebels, pro-government forces stepped up their attacks on the Eastern Ghouta, reportedly with Russian air support.

Since then, at least 151 civilians have been killed by air strikes and shelling, according to the Syrian Observatory for Human Rights. The UK-based monitoring group said four people had died in the town of Hamouria on Tuesday.

State media say rebel shellfire has also killed civilians in neighbouring areas.

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Activists said air strikes on the town of Hamouria killed at least four people on Tuesday

It said they had dealt with 576 wounded patients and 69 dead - a quarter of them women and children - and that the true figures were unquestionably higher.

The organisation added that a major field hospital in Kafr Batna was hit by two rockets on 20 November, seriously damaging hospital infrastructure and putting one ambulance out of service, while another two field hospitals and a clinic temporarily suspended non-emergency services between 15 and 18 November out of fear of exposing medics and patients to danger.

MSF said most facilities were in urgent need of fresh medical supplies, and warned that patients' lives would be at stake if they were not replenished.

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A joint UN-Syrian Red Crescent convoy reached the town of Nashabieh on Tuesday

UN agencies say food shortages have led to a growing number of acutely malnourished children, and limited electricity, fuel, safe drinking-water and basic sanitation services are increasing the risk of outbreaks of diarrheal diseases.